Nonlinear static and dynamic properties of Metal Rubber dampers

Metal Rubber (MR) is a form of a metallic mesh that is manufactured via a process of wire-drawing, weaving and compression moulding. The term Metal Rubber arises from the similarity between the properties of MR and those of rubber. MR offers the potential to be a good damping material at both low and high temperature regimes which makes it a strong candidate for applications in extreme environments. It is shown experimentally that the stiffness of MR dampers is affected by the structural parameters of the metal mesh including its relative density, wire diameter and typical coil size. It is also found that the effective Poisson's ratio for MR is zero. As MR is normally used in a pre-compressed condition, a test rig was constructed that allowed the dynamic stiffness of MR elements to be tested over a range of amplitudes, frequencies and precompression levels. The rig comprised a rigid base to which a stiff metal tube was mounted using MR elements. The properties of the MR elements were estimated from their effects on the rigid body modes of the tube. The mass of the tube and excitation levels were varied to achieve different dynamic strain amplitude and frequency levels on the MR elements. Results show that the dynamic properties of MR are highly nonlinear and strongly affected by precompression. Similarities and differences in performance between MR and elastomeric materials are highlighted through experimental comparison.